This invention relates to refrigeration systems, and more particularly to an improved, more highly efficient refrigeration system for refrigerated display cases wherein at least a portion of the cooled air which spills from the refrigerated display cases is utilized to subcool liquid refrigerant prior to expansion in the system.
In recent years the escalating cost of energy has caused additional attention to be focused on improving the efficiency of energy consuming systems of various types. The impetus to reduce costs by reducing energy consumption has carried over to retail supermarket operations, wherein significant amounts of energy are consumed in providing continuous refrigeration for dairy, meat, and other perishable products including frozen foods and related items. In addition, the modern supermarket includes a year-round air conditioning system to maintain proper temperature and humidity for the comfort of shoppers.
Such high energy usage equipment provides a fertile field for possible cost savings through the more efficient use of the energy involved. One approach is shown in U.S. Pat. No. 4,285,205, which issued Aug. 25, 1981 to Leonard I. Martin et al., and which discloses a refrigerant subcooling arrangement for use in a refrigeration system having a central compressor and condenser arrangement and a plurality of remotely located evaporators. In the system described in that patent a heat exchanger is provided to permit heat interchange between the warm, liquid refrigerant and the relatively cool, gaseous refrigerant to increase the suction gas temperature of the refrigerant entering the compressor and to subcool the liquid refrigerant before it enters the respective evaporators.
Another approach to the problem of minimizing energy consumption in a supermarket refrigeration and air conditioning system is disclosed in U.S. Pat. No. 4,176,525, granted Dec. 4, 1979 to James M. Tucker et al. In that patent an integrated refrigeration and air conditioning arrangement is disclosed wherein various control arrangements are provided to properly maintain interior conditions regardless of the weather and the season. One aspect of the Tucker et al. disclosure relates to refrigerant subcooling wherein ambient air within the store is passed over an additional condenser to provide cooling of the warmer liquid refrigerant below the temperature at which it exits from the main condenser.
It is an object of the present invention to provide an improved, energy efficient system wherein additional subcooling of the liquid refrigerant is effected without any increase in energy usage in order to improve refrigeration efficiency and thereby reduce operating costs.